Fiber distribution frame with fiber termination blocks

ABSTRACT

A fiber termination block including a frame structure adapted to be connected to a fiber distribution rack. The frame structure includes a front end and a rear end. A front fiber optic adapter array is positioned adjacent the front end of the frame structure. A plurality of rear modules are mounted at the rear end of the frame structure. Each of the rear modules defines a front opening. At least one coupler is mounted within each of the rear modules. A plurality of fiber optic cables are provided for transmitting fiber optic signals between the front fiber optic adapter array and the couplers. The fiber optic cables extend through the front openings of the rear modules to access the couplers.

FIELD OF THE INVENTION

[0001] The present invention relates generally to telecommunicationsequipment. More particularly, present invention relates to high-densityfiber distribution frames including fiber termination blocks.

BACKGROUND OF THE INVENTION

[0002] In the telecommunications industry, the use of fiber optic cablesfor carrying transmission signals is rapidly growing. To interconnectfiber optic equipment, fiber distribution frames have been developed.Examples of fiber distribution frames are shown in commonly assignedU.S. Pat. Nos. 5,497,444 and 5,758,003, which are hereby incorporated byreference.

[0003] With the increase in use of fiber optic cables in thetelecommunications industry, it is desirable to provide fiberdistribution frames with increased density. By density, it is meant thenumber of locations per unit volume or unit area for providingconnection on the fiber distribution frame.

[0004] The space constraints associated with high-density distributionframes can cause cable management problems. Effective cable managementprevents excessive bending of fiber optic cables within the frames.Effective cable management also minimizes tangling of cables, andprovides improved accessibility to components that may requireservicing.

[0005] It is an object of the present invention to provide a fiberdistribution frame that permits high density, ready access and enhancedfiber management.

SUMMARY OF THE INVENTION

[0006] One aspect of the present invention relates to a fibertermination block that includes a frame structure adapted to beconnected to a fiber distribution rack. The frame structure includes afront end and a rear end. A front fiber optic adapter array ispositioned adjacent the front end of the frame structure. A plurality ofrear modules is mounted at the rear end of the frame structure. Each ofthe rear modules defines a front opening. At least one coupler ismounted within each of the rear modules. A plurality of fiber opticcables is provided for transmitting fiber optic signals between thefront fiber optic adapter array and the couplers. The fiber optic cablesextend through the front openings of the rear modules to access thecouplers.

[0007] Another aspect of the present invention relates to a fiber opticmodule that is adapted to be connected to a fiber optic distributionframe. The fiber optic module includes a housing having two spaced-apartmajor sides interconnected by two spaced-apart minor sides. The majorand minor sides extend between front and rear ends of the housing. Thefront end of the housing defines a front opening through which aplurality of fiber optic cables can pass. The module also includesstructure for connecting the housing to the distribution frame, aplurality of fiber optic adapters mounted at the rear end of thehousing, and a plurality if indicator lights mounted at the front end ofthe housing. A fiber optic coupler is mounted within the housing and atleast one radius limiter is positioned near the front opening of thehousing. The radius limiter limits the bending radiuses of the fiberoptic cables that pass through the opening.

[0008] A further aspect of the present invention relates to a fiberdistribution apparatus including a rack having a front side and a rearside. A front fiber optic adapter array is positioned adjacent the frontside of the rack, and a plurality of rear modules is mounted at the rearside of the rack. Each of the rear modules defines a front opening. Atleast one coupler mounted within each of the rear modules, and aplurality of fiber optic cables is provided for transmitting fiber opticsignals between the front fiber optic adapter array and the couplers.The fiber optic cables extend through the front openings of the rearmodules to access the couplers.

[0009] A variety of advantages of the invention will be set forth inpart in the description that follows, and in part will be apparent fromthe description, or may be learned by practicing the invention. It is tobe understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate several aspects ofthe invention and together with the description, serve to explain theprinciples of the invention. A brief description of the drawings is asfollows:

[0011]FIG. 1 is a front perspective view of a fiber distribution rackconstructed in accordance with the principles of the present invention;

[0012]FIG. 2 is a rear perspective view of the fiber distribution rackof FIG. 1;

[0013]FIG. 3 is a partial front view of the fiber distribution rack ofFIG. 1 with a fiber termination block secured thereto;

[0014]FIG. 4 is a rear perspective view of the rack and terminationblock of FIG. 3;

[0015]FIG. 5 is a rear view of the rack of FIGS. 1 and 2 with a cablemanagement route schematically depicted;

[0016]FIG. 6 is a perspective view of a fiber termination blockconstructed in accordance with the principles of the present invention;

[0017]FIG. 7 is a rear perspective view of the fiber termination blockof FIG. 6;

[0018]FIG. 8 is a partially exploded, perspective view of the fibertermination block of FIG. 6;

[0019]FIG. 9 is a perspective view of the fiber termination block ofFIG. 6 with the front door open and one of the sliding adapter packsslid laterally outward;

[0020]FIG. 10 is a rear view of the fiber termination block of FIG. 6;

[0021]FIG. 11 is a rear perspective view of a rear adapter moduleconstructed in accordance with the principles of the present invention;

[0022]FIG. 12 is a front perspective view of the rear adapter module ofFIG. 11;

[0023]FIG. 13 is a top view of the rear adapter module of FIG. 11 withthe side panel removed and a cable management configuration schematicshown therein; and

[0024]FIG. 14 illustrates a schematic cross-connect circuitconfiguration showing exemplary signal paths for main signals (solid)and for continuity check and identifier signals (dashed).

DETAILED DESCRIPTION

[0025] Reference will now be made in detail to exemplary aspects of thepresent invention that are illustrated in the accompanying drawings.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts. With initial referenceto FIG. 1, a fiber distribution apparatus 10 (i.e., a rack, frame, bay,etc.) is shown including a support frame 12 mounted on a base member 14.The frame 12 includes spaced-apart and parallel vertical support posts16,17 extending the height of the frame 10. The support posts 16,17 areconnected at their upper ends by a cross-brace 13. On the front side ofthe frame 12, a vertical and centrally positioned trough 20 is provided.The trough 20 is vertically aligned and has a U-shaped cross-sectionthat opens toward the front of the frame 12. A back wall of the trough20 is rigidly secured to the top brace 13. The base 14 includes a basetrough 22 that is positioned below and is accessible from the verticaltrough 20.

[0026] Positioned within the vertical trough 20 is a plurality of spools24. Radius limiters 26 are provided at the lower terminal end of thevertical trough 20. The radius limiters 26 are capped with clips 28 topermit passage of fiber optic cables between the spacing of the clips 28and into the vertical trough 20 such that fibers can be passed from thebase trough 22 into the vertical trough 20.

[0027] Referring to FIG. 2, the backside of the fiber distributionapparatus 10 also includes a centrally located, vertical trough 320. Aplurality of vertically spaced-apart spools 324 is positioned within thetrough 320. A rear base opening 318 is positioned beneath the verticaltrough 320 for use in allowing cable to pass through the base 14 inraised floor applications. Radius limiting guides 323 are provided forguiding fiber optic cable fed to and from the vertical trough 320. Abase plate 319 protects fiber optic cables routed adjacent to the bottomof the frame 14.

[0028] Still referring to FIG. 2, vertically spaced-apart horizontaltroughs 325 are positioned on left and right sides of the verticaltrough 320. Each of the horizontal troughs 325 is connected to a guidering 327 by a downwardly curved radius limiter 333. The guide rings 327are arranged to define vertical channels positioned on opposite sides ofvertical trough 320. A set of five vertically spaced-apart fanningmembers 329 is positioned above the outer end portion of each of thehorizontal troughs 325. The fanning members 329 have curved surfacesthat function as bending radius limiters. The curved surface of thelowermost fanning member of each set face downwardly, while the curvedsurfaces of the remainder of the fanning members of each set faceupwardly. A cable retaining flange 337 is located at the far end of eachfanning member 329. Shielding plates 331 are positioned outside thefanning members 329.

[0029] The frame 12 is configured to hold or support a plurality offiber termination blocks. Preferably, the fiber termination blocks aremounted on the frame 12 so as to form separate vertical rows located onopposite sides of the central trough 20. FIGS. 3 and 4 show arepresentative fiber termination block 30 mounted on the right side ofthe vertical trough 20. It will be appreciated that fiber terminationblocks mounted on the left side of the vertical trough preferably areconstructed in the mirror image of the termination block 30. The fibertermination block 30 preferably includes a lateral flange 33 (best shownin FIGS. 4 and 7) positioned to align with a corresponding flange 35(best shown in FIGS. 1 and 4) of the frame 12. To secure the terminationblock 30 to the frame 12, fasteners (e.g., screws, bolts, etc.) are usedto connected the two flanges 33, 35 together. However, it will beappreciated that any type of connection arrangement could be used.

[0030]FIG. 5 shows a rear view of the fiber distribution apparatus 10with the fiber termination block 30 mounted on the frame 12. Arepresentative fiber optic cable 340 is shown connected to a rearadapter array 342 of the termination block 30. As shown in FIG. 5, thecable 340 is guided by numerous cable management structures. Forexample, the cable 340 extends between two of the fanning members 329downward to the horizontal trough 325. The cable 340 then extends acrossthe trough 325, and down the channel defined by rings 327 toward thebottom of the frame 12. Excess cable is managed by looping the excesscable about the spools 324 in the rear vertical channel 320. From thevertical channel 320, the cable can extend under radius limiter 323 andupward through rings 327 to the top of the frame 12 for overhead cableentry/exit.

[0031] FIGS. 6-10 show the fiber termination block 30 in isolation fromthe frame 12. The termination block 30 includes a support frame 36 thatdefines a front housing 37 and a rear housing 39. A plurality of frontadapter modules 38 (i.e., sliding adapter packs) are mounted within thefront housing 37. Each of the front adapter modules 38 includes a row offiber optic adapters 41 mounted on an elongated support structure 43.The rows of adapters 41 form a front adapter array 51 (best shown inFIGS. 8 and 9) that includes a plurality of rows and columns ofadapters. The support structures 43 are mounted within guides 45connected to the frame 36. The guides 45 allow the front adapter modules38 to individually slide in a direction transverse relative to alongitudinal axis L of the termination block 30 (e.g., horizontally asshown in FIG. 9). This individual sliding action makes the adapters 41more accessible. Pivoting locks 47 prevent the adapter modules 38 frominadvertently sliding. Further details concerning the adapter modules 38are provided in the aforementioned '444 patent, which was previouslyincorporated by reference.

[0032] The fiber optic adapters 41 permit the connection of fiber opticcables to the front sides of the modules 38. The adapters 41 alsoprovide locations for connecting fiber optic cables to the rear of eachmodule 38. Fiber optic cables connected to the front of the modules 38will extend away from the front faces of the modules 38 in a directiongenerally perpendicular to a plane defined by posts 16,17. To directsuch fiber optic cables rearwardly, the cables first extend betweenfanning members 39, and then extend downwardly around a radius limiter40 and rearwardly through a lower retaining clip 42. The cables thenextend rearwardly through a horizontal trough 77 provided on thedistribution apparatus 10 (shown in FIG. 1), and laterally throughpassage 79 toward the center of the rack. After passing through passage79, the cables extend downwardly through vertically spaced-apart rings81. If it is desired to provide cross-connections with circuits at theopposite side of the frame 12, the cables are looped under radiuslimiters 26, routed to the other side of the frame, and extended upthrough rings 81 to the desired cross-connect location. Excess cable canbe managed by wrapping the cable around the spools 24 of the verticaltrough 20 in the same manner shown in FIG. 5. If it is desired toprovide cross-connections with another distribution apparatus, thecables preferably exit the distribution apparatus through trough 22.

[0033] To protect the looped fiber optic cables at the front of eachfiber termination block 30, hinged doors or covers 44 are secured to theframe 36 such that the covers 44 protect the looped cables extendingfrom modules 38 and around radius limiter 40. The doors 44 may be openedby pivoting along their vertical hinges 45 to permit increased ease ofaccess to the adapter modules 38.

[0034] The rear housing 39 of the termination block 30 defines a cavityor bay 48 sized to receive a plurality of rear adapter modules 50. Thebay 48 is generally rectangular and is defined between two spaced-apartvertical walls 52 and 54. A removable cover 56 encloses the top of thebay 48, and a base 58 defines the bottom of the bay 48.

[0035] As best shown in FIGS. 8-10, the rear adapter modules 50 arevertically stacked within the bay 48. For example, as shown in thedrawings, the bay 48 is sized to receive four of the adapter modules 50.However, it will be appreciated that the number of modules can be variedwithout departing from the principles of the present invention. Anynumber of conventional techniques can retain the rear adapter modules 50within the rear housing 39. For example, the modules can be secured tothe rear housing 39 by fasteners (e.g., screws, bolts, etc.), clips,latches, etc. As shown in FIG. 8, the modules 50 are secured (e.g., byfasteners) to a vertical support 53 mounted between the base 58 and thecover 56 of the rear housing 39 (e.g., by fasteners). The front of thevertical support 53 is covered by a removable vertical edge protector 55having a curved front surface and rear edges that fit withincorresponding slots 57 defined by the front sides of the modules 50. Theedge protector 55 can be removed to access the fasteners used to securethe modules 50 to the vertical support 53. The back side of the rearhousing 39 is preferably open such that the rear adapter modules 50 canbe inserted from the back side of the termination block 30 into the bay48, and pushed into abutment with the vertical support 53.

[0036] As shown in FIG. 10, each of the rear adapter modules 50 includesan array of fiber optic adapters 60 arranged in rows and columns. Theadapters 60 of the four rear adapter modules 50 collectively form therear adapter array 342 of the entire termination block 30. The rearadapter array 342 is divided into first and second regions 342 a and 342b by a step 344. The step 344 provides an offset that recesses thesecond region 342 b further into the rear housing 39 than the firstregion 342 a. The adapters 60 of each of the regions 342 a and 342 b aremounted on surfaces aligned at oblique angles relative to thelongitudinal axis L of the fiber termination block 30.

[0037] Referring to FIG. 8, each of the rear adapter modules 50 includesan array of indicator lights 346 (e.g., light-emitting diodes) for usein tracing cross-connected signals. The indictor lights 346 are locatedat the front of each module 50, and face toward the front of thetermination block 30. Preferably, the indicator lights 346 are laterallyoffset with respect to the front adapter array 51. Thus, when atechnician views the front of the fiber termination block 30, theindicator lights 346 are not obstructed by the front adapter modules 38of the front adapter array 51. However, when the front adapter modules38 are slid laterally outward from the guides 45, the adapter modules 38do at least partially block portions of the array of indicator lights346 from view.

[0038] With the structure thus described, a plurality of fiber opticcables (e.g., cables from equipment) can be coupled to the rear adapterarrays 342. Additional fiber optic cables are routed from the rearadapter array 342 through the rear adapter modules 50 to the frontadapter modules 38. In certain embodiments, couplers (e.g., splitters,combiners, wave division multi-plexers, etc.) can be provided within therear adapter modules 50 for providing a desired cable routingconfiguration between the rear adapter array 342 and the front adapterarray 51. In extending from the rear adapter modules 50 to the frontadapter modules 38, the cables pass through an intermediate regiondefined by the support frame 36 of the fiber termination block 30. Theintermediate region includes a plurality of fanning members 350 (shownin FIG. 8) that facilitate cable management within the intermediateregion. A side panel 352 encloses the intermediate chamber 348. The sidepanel 352 includes a plurality of slots 354 that provide clearance forallowing fiber optic cables connected to the front adapter modules 38 topass through the side panel 352 when the front adapter modules 38 areslid laterally from the guides 45.

[0039]FIGS. 11 and 12 show one of the rear adapter modules 50 inisolation from the fiber termination block 30. The depicted rear adaptermodule 50 includes a housing 356 having two spaced-apart major sides 358interconnected by two spaced-apart minor sides 360. The major and minorsides 358 and 360 extend between front and back ends 362 and 364 of theadapter module 50. The fiber optic adapters 60 are mounted at the backend 364 of the rear adapter module 50. For example, the adapters 60 areshown mounted at first and second surfaces 366 and 368 that aresubstantially parallel to one another. A staggering member 370 extendstransversely between the first and second surfaces 366 and 368 toprovide a connection thereinbetween. The adapters 60 are preferablyremovably connected to the housing 356. For example, the adapters 60 canbe snap fit within clips 69 that are snapped within the rear of thehousing 356.

[0040] Referring to FIG. 12, the rear adapter module 50 also includes afront wall 380 defining an opening 382 sized for allowing a plurality offiber optic cables to pass therethrough. Radius limiters 384 that limitthe amount the fiber optic cables passing through the opening 382 canbend define top and bottom sides of the opening. The front wall 380 alsoincludes a panel portion 386 at which the array of indicator lights 346is mounted. In certain embodiments, the indicator lights 346 can beeliminated.

[0041] As shown in FIG. 11, the depicted embodiment includes 12adapters. The adapters 60 are arranged in pairs with each pair defininga transmit input port (Tx_(in)) and a receive output port (Rx_(out)). Byway of example, adapters 388 and 390 represent one such pair. Each pairof adapters 60 corresponds to a separate fiber optic circuit. Each ofthe six circuits has a corresponding indicator light 346 positioned atthe front of the rear adapter module 50 for use in tracing cross-connectsignals transmitted through the circuits.

[0042] The pairs of rear adapters 60 can be optically coupled to thefront adapters 41 by fiber optic cables. Preferably, couplers 392 (shownin FIG. 13) are positioned within the rear adapter module 50 to providean end user with desired optical routing pathways or configurations. Asshown in FIG. 13, the plurality of couplers 392 are mounted within theadapter module 50 by a bracket structure 63 secured to one of the minorsides 360 of the rear adapter module 50.

[0043]FIG. 13 shows a strictly representative routing configuration forconnecting the Tx_(in) and Rx_(out) ports of one of the pairs of rearadapters 60 to corresponding transmit output and receive input ports(Tx_(out) and Rx_(in)) provided at one of the front adapter modules 38.As shown in FIG. 13, the Rx_(out) port is hidden behind the Tx_(in)port. The Tx_(in) signal from the Tx_(in) port is split by one of thecouplers 392 such that the signal is also directed to a transmit monitorport Tx_(monitor) at the front adapter module 38, and an indicator lightID_(out) at the front of the rear adapter module 50. The Rx_(in) signalfrom the Rx_(in) port is split by one of the couplers 392 such that thesignal is also directed to a receive monitor port Rx_(monitor) at thefront adapter module 38. The fiber optic cables within the rear module50 are looped around guides 393 within the module 50 to enhance cablemanagement.

[0044] While the couplers 392 have been shown as splitters, it will beappreciated that different types of couplers can be varied to achievedesired routing configurations. Additionally, while only one circuit hasbeen shown in the module 50 for clarity, it will be appreciated thatfibers for each of the six different optical circuits can be providedwithin the rear module 50. Further, in certain embodiments, it may bedesired to by-pass the couplers 392 and provide straight pass throughsthrough the rear module 50. In still other embodiments, the rearadapters 60 can be eliminated, or replaced with blanks, such that therear module 50 functions solely to house couplers that are accessedthrough the front opening 382. While six pairs of adapters 60 have beenshown mounted on the rear module 50, it will be appreciated that anynumber of adapters could be used depending upon the needs of an enduser.

[0045] An important use of the fiber termination blocks 30 is to providecross connections between two different fiber optic circuits (e.g.,fiber optic circuits from different racks). Generally, in across-connect application, the rear adapters 60 are connected to fiberoptic equipment to be cross-connected at the front adapters 41 throughpatch cords. The two circuits each allow optical signal routing,monitoring and signal path identification. FIG. 14 illustrates thecircuit paths between a first circuit 400 a and a second circuit 400 bduring main signal usage (shown in solid line), and during visualcontinuity check and identifier usage (shown in dashed line). Mainsignals are at the 1310 nanometer (nm) window (e.g., 1260-1360 nm) orthe 1550 nm window (e.g., 1430-1580 nm). During visual continuitychecking and identification, the identification signals are passedthrough the circuits in a reverse direction to the main signals.Further, the identification signals are at a wavelength of visiblelight, such as 400-700 nm.

[0046] A rear adapter module 50 a and a front connector module 38 a formthe first circuit 400 a; and a rear adapter module 50 b and a frontconnector module 38 b form the second circuit 400 b. The rear adaptermodule 50 a includes an Rx_(out) port 404 a, a Tx_(in) port 406 a, andan indicator light 408 a. The front connector module 38 a includes anRx_(in) port 410 a, an Rx_(mon) 412 a, a Tx_(mon) port 414 a and aTx_(in) port 116 a. The rear module 50 b includes an Rx_(out) port 404b, a Tx_(in) port 406 b, and an indicator light 408 b. The frontconnector module 38 b includes an Rx_(in) port 410 b, an Rx_(mon) port412 b, a Tx_(mon) port 414 b and a Tx_(out) port 416 b. A first crossconnect cable 420 (e.g., a patch cord or a jumper cable) provides aconnection between the Rx_(in) port 410 a and the Tx_(out) port 416 b.Also, a second cross connect cable 422 provides a fiber optic connectionbetween the Tx_(out) port 416 a and the Rx_(in) port 410 b.

[0047] A main signal inputted (e.g., from equipment) at the Tx_(in) port406 a travels through the module 50 a to the Tx_(out) port 416 a of thefront connector module 38 a. From the Tx_(out) port 416 a, the signaltravels through cross connect cable 422 to the Rx_(in) port 410 b of thefront connector module 38 b. Thereafter, the signal travels from theRx_(in) port 410 b to the Rx_(out) port 404 b where the signal isoutputted to equipment.

[0048] To trace the main signal described above, a tracing signal can beinjected through the Rx_(mon) port 412 b. The injected signal followsthe pathway defined by the main signal through the cross connect cable422 to the first module 50 a where the tracing signal is output at theindicator light 408 a.

[0049] The second main signal is input at Tx_(in) port 406 b (e.g., fromequipment) and is transmitted to the Tx_(out) port 416 b of the frontconnector module 38 b. From the Tx_(out) port 416 b, the signal istransmitted by the cross connect cable 420 to the Rx_(in) port 410 a ofthe front connector module 38 a. From the front connector module 38 a,the signal travels to the Rx_(out) port 404 a where the signal isoutputted to equipment.

[0050] To trace the second main signal, a tracing signal can be injectedinto the Rx_(mon) port 412 a. The injected signal travels in a reversedirection along the pathway defined by the second main signal and isoutput at the indicator light 408 b of the second module 50 b.

[0051] As described above, the tracing signals are injected through themonitor ports. Alternatively, separate ports can be linked to thereceive output lines (e.g., by couplers such as splitters) for use ininjecting tracing signals through the cross-connect circuits. Also,couplers 450 a and 452 a are used to split signals at the first module50 a, and couplers 450 b and 452 b are used to split signals at thesecond module 50 b. It will be appreciated that the couplers 450 a, 452a, 450 b and 452 b can have any number of conventionally knownconfigurations, and are preferably adapted to allow the identificationsignals to pass in the reverse direction to the main signals. Also, theadapters described herein can have any number of known adapterconfigurations (e.g. FC type adapters, SC type adapters, ST typeadapters, etc.)

[0052] With regard to the foregoing description, it is to be understoodthat changes can be made in detail, especially in matters of theconstruction materials employed and the shape, size and arrangement ofthe parts without departing from the scope of the present invention. Itis intended that the specification and the depicted aspects beconsidered exemplary only, with a true scope and spirit of the inventionbeing indicated by the broad meaning of the following claims.

We claim:
 1. A fiber termination block comprising: a frame structureadapted to be connected to a fiber distribution rack, the framestructure including a front end and a rear end and a longitudinal axisthat extends between the front and rear ends; a plurality of slidingadapter packs positioned adjacent the front end of the frame structure,each of the adapter packs including a row of front fiber optic adapters,the rows of fiber optic adapters being arranged in a forwardly facingarray, the sliding adapter packs being slidable in a directiontransverse with respect to the longitudinal axis of the frame structureto facilitate accessing the adapter packs; a plurality of rear modulesmounted at the rear end of the frame structure, the rear modulesincluding a plurality of rear fiber optic adapters arranged in arearwardly facing array; a plurality of fiber optic cables fortransmitting fiber optic signals between the front fiber optic adaptersand the rear fiber optic adapters; and at least one coupler mountedwithin each of the rear modules through which at least some of thesignals carried by the fiber optic cables are routed.
 2. The fibertermination block of claim 1, wherein the rear modules each include atleast one rear wall positioned opposite from a front wall, wherein therear fiber optic adapters are mounted at the rear walls, and wherein thefront walls each define an opening through which the fibers pass toextend from the rear modules to the sliding adapter packs.
 3. The fibertermination block of claim 2, further comprising a plurality ofindicator lights positioned at the front walls of the rear modules andlinked to at least some of the fiber optic cables.
 4. The fibertermination block of claim 3, wherein the indicator lights are laterallyoffset from the forwardly facing array defined by the forward adapters,a wherein the lateral offset permits the indicator lights to be vieweddirectly from the front end of the frame structure without interferencefrom the forward adapters.
 5. The fiber termination block of claim 2,further comprising radius limiters for guiding the fiber optic cablesthrough the openings in the front walls.
 6. A fiber termination blockcomprising: a frame structure adapted to be connected to a fiberdistribution rack, the frame structure including a front end and a rearend; a front fiber optic adapter array positioned adjacent the front endof the frame structure; a plurality of rear modules mounted at the rearend of the frame structure, each of the rear modules defining a frontopening; at least one coupler mounted within each of the rear modules;and a plurality of fiber optic cables for transmitting fiber opticsignals between the front fiber optic adapter array and the couplers,the fiber optic cables extending through the front openings of the rearmodules to access the couplers.
 7. The fiber termination block of claim6, wherein the rear modules each include a plurality of rear fiber opticadapters arranged in a rearwardly facing array, the rear fiber opticadapters being coupled to at least some of the fiber optic cables. 8.The fiber termination block of claim 6, further comprising radiuslimiters positioned at the front openings of the rear modules forlimiting the bending radiuses of the fiber optic cables passing throughthe front openings.
 9. The fiber termination block of claim 7, furthercomprising a plurality of indicator lights positioned at a front end ofeach rear module for tracing cross connect signals.
 10. The fibertermination block of claim 6, further comprising a plurality of cablemanagement guides positioned within the rear modules.
 11. The fibertermination block of claim 9, wherein one of the rear fiber opticadapters is optically coupled to a transmit output port and a transmitmonitor port of the front fiber optic adapter array and is alsooptically coupled to one of the indicator lights; and another of therear fiber optic adapters is optically coupled to a receive input portand a receive monitor port of the front fiber optic adapter array.
 12. Afiber optic module adapted to be connected to a fiber optic distributionframe, the fiber optic module comprising; a housing including twospaced-apart major sides interconnected by two spaced-apart minor sides,the major and minor sides extending between front and rear ends of thehousing, the front end of the housing defining a front opening sized forallowing a plurality of fiber optic cables to pass therethrough;structure for connecting the housing to the distribution frame; aplurality of fiber optic adapters mounted at the rear end of thehousing; a plurality if indicator lights mounted at the front end of thehousing; a fiber optic coupler mounted within the housing; and at leastone radius limiter positioned near the front opening of the housing forlimiting the bending radiuses of the fiber optic cables that passthrough the opening.
 13. The fiber optic module of claim 12, wherein thecoupler is secured to one of the minor sides of the housing.
 14. Thefiber optic module of claim 12, further comprising cable managementguides mounted within the housing.
 15. A fiber distribution apparatuscomprising: a rack having a front side and a rear side; a front fiberoptic adapter array positioned adjacent the front side of the rack; aplurality of rear modules mounted at the rear side of the rack, each ofthe rear modules defining a front opening; at least one coupler mountedwithin each of the rear modules; a plurality of fiber optic cables fortransmitting fiber optic signals between the front fiber optic adapterarray and the couplers, the fiber optic cables extending through thefront openings of the rear modules to access the couplers.
 16. The fiberdistribution apparatus of claim 15, wherein the rear modules eachinclude a plurality of rear fiber optic adapters arranged in arearwardly facing array, the rear fiber optic adapters being coupled toat least some of the fiber optic cables.
 17. The fiber distributionapparatus of claim 15, further comprising radius limiters positioned atthe front openings of the rear modules for limiting the bending radiusesof the fiber optic cables passing through the front openings.
 18. Thefiber distribution apparatus of claim 16, further comprising a pluralityof indicator lights positioned at a front end of each rear module fortracing cross connect signals.
 19. The fiber distribution apparatus ofclaim 15, further comprising a plurality of cable management guidespositioned within the rear modules.
 20. The fiber distribution apparatusof claim 15, wherein the rack includes centrally located, vertical cablemanagement troughs located at both the front side and the rear side ofthe rack, and wherein each of the troughs includes cable managementspools.
 21. The fiber distribution apparatus of claim 20, wherein atboth the front side and the rear side the rack includes two verticalcable management channels positioned on opposite sides of the centrallylocated vertical troughs.
 22. The fiber distribution apparatus of claim21, wherein the vertical channels are defined by a plurality ofvertically spaced-apart rings.
 23. The fiber distribution apparatus ofclaim 22, wherein the rear side of the rack includes a plurality ofvertically spaced-apart horizontal troughs, each of the troughsincluding a radius limiter member that connects with one of the rings.